1. Field of the Invention
This invention relates to polymeric tubings and more particularly to medical grade tubings for clinical use.
2. Description of the Prior Art
The use of polymeric tubings in medical or clinical applications is well known. In general, such tubings are made of natural or synthetic polymeric materials. Since the tubings come in contact with human tissues or body fluids, stringent requirements must be met for medical applications. These requirements vary, depending on the nature of the application.
Numerous techniques have been developed to assist or replace the failing heart. The methods of assistance utilized vary with the degree and duration of ventricular dysfunction. In general, the most common type of cardiac assistance comprises pumping the blood from the patient, feeding the blood to an oxygenator and returning the oxygenated blood back to the patient. The pump most commonly used is a roller pump.
FIG. 1 shows a typical roller pump 10 where a tubing 12 is compressed by a rotating arm 14 having a roller 16 at each end. Rotating arm 14 which rotates about hub 18 exerts gentle mechanical action on the blood so as not to damage the blood.
It is evident that in selecting the tubing material for use in a roller pump several physical characteristics for the material must be considered carefully. Such characteristics include: (1) rebounding of tubing (volume vs revolutions per minute); (2) rebounding over time with continuous pumping; (3) flex life; and (4) spallation (i.e. tubing debris produced by pumping). Among these, spallation is particularly important in that for obvious reasons the production of debris as a result of pumping should be kept to a minimum so as to avoid the introduction of foreign matters into the patient's blood.
The materials most commonly used in the production of medical grade tubings include polyvinyl chloride, silicone rubber and synthetic rubber. However, these materials have been found to be unsatisfactory in that they either have short flex life or high spallation. Hence, there is a need for a polymeric material which possesses long flex life and low spallation for the manufacture of medical grade tubings, particularly tubings useful in cardiac assistance equipment.